package com.wp.targetOffer;

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.Queue;

/**
 * Created by 王萍 on 2017/8/14 0014.
 */
public class 按层打印二叉树 {

    public static void main(String[] args) {
        TreeNode node1 = new TreeNode(1);
        TreeNode node2 = new TreeNode(2);
        TreeNode node3 = new TreeNode(3);
        TreeNode node4 = new TreeNode(4);
        TreeNode node5 = new TreeNode(5);
        TreeNode node6 = new TreeNode(6);
        TreeNode node7 = new TreeNode(7);

        node1.left = node2;
        node1.right = node3;
        node2.left = node4;
        node2.right = node5;
        node3.left = node6;
        node3.right = node7;

        PrintFromTopToBottom(node1).stream().forEach(s -> System.out.print(s + " "));
    }

    public static ArrayList<Integer> PrintFromTopToBottom(TreeNode root) {
        ArrayList<Integer> list = new ArrayList<>();
        if (root == null) return list;

        Queue<TreeNode> queue = new LinkedList();
        queue.offer(root);
        while (!queue.isEmpty()) {
            TreeNode node = queue.poll();
            list.add(node.val);
            if (node.left != null) queue.offer(node.left);
            if (node.right != null) queue.offer(node.right);
        }
        return list;
    }

    private static class TreeNode {
        int val = 0;
        TreeNode left = null;
        TreeNode right = null;

        public TreeNode(int val) {
            this.val = val;
        }
    }
}
